A day after a massive engine failure on the world's largest jetliner, manufacturer Rolls-Royce watched a billion dollars vanish from its market value, while another of its engines on a different plane caught fire in flight.
The Australian airline Qantas blamed the British aerospace company for the violent mid-flight disintegration on Thursday of an engine on the Airbus A380. Another Qantas plane equipped with Rolls-Royce engines suffered an engine problem shortly after takeoff late Friday, producing a loud bang and shooting fire before it turned back to Singapore.
Modern passenger jets are designed to fly after one or more engine failures, and both Qantas planes landed safely.
On Thursday, one of the A380's four Rolls-Royce Trent 900 engines failed minutes into a flight to Sydney, shedding pieces of metal over Indonesia before it returned to make a safe emergency landing in Singapore.
"We believe this is probably most likely a material failure or some type of design issue," Qantas CEO Alan Joyce told a news conference in Sydney. "We don't believe this is related to maintenance in any way." Joyce said the engines had been maintained by Rolls-Royce since they were installed.
Rolls-Royce Group PLC, a London-based aerospace, power systems and defense company separate from the car manufacturer, made no public comment. Its stock price took a beating for the second day, ending more than 5 percent lower.
Experts said an engine flaw could be responsible, with one pointing to a shattered piece of turbine as the possible failure point.
Qantas' has six of the double-decker Airbus A380s, the world's largest and newest airliner.
It is as tall as a seven-story building and capable of carrying 853 passengers, although most airlines use it for about 500 passengers. Its roomy first and business classes are seen as a major appeal for passengers.
Twenty planes operated by Qantas, Lufthansa and Singapore Airlines use the Trent 900. One of the newest and largest airline engines, the Trent 900 is an immensely powerful and highly complex piece of equipment as tall as a single-story house.
The engine on the Qantas Airbus suffered what aviation experts call an uncontained engine failure, in which high-energy debris from the rotating parts break through the engine casing.
Such accidents, rare these days due to improvements in design and the metallurgy, usually are caused by engines sucking in objects like runway debris or a bird, or maintenance crews failing to replace parts that wear out.
"The possible danger of an uncontained failure is shrapnel from the turbines or compressors exiting the engine case and puncturing portions of the wing and fuselage," said Patrick Smith, a commercial airline pilot and aviation author. "A worse-case scenario could have pieces of hot metal going into the fuel tanks or into the cabin, causing a leak or fire or cabin depressurization."
Late Friday, a Sydney-bound Qantas Boeing 747-400 fitted with four Rolls-Royce RB211-524G-T engines landed safely in Singapore after an engine caught fire minutes after it took off, the airline said.
"There was a loud bang and a jet of fire from the back of the engine," passenger Andrew Jenkins, a 43-year-old Australian banker, told The Associated Press.
Jenkins said he could see the engine clearly and the blast happened "one or two minutes" into the flight when the plane with 431 people aboard had climbed about 2,000 feet.
The passengers were being put up in hotels and would be brought to Australia on flights arriving Sunday, Qantas said.
William Voss, head of the Flight Safety Foundation based in Alexandria, Virginia, said the latest incident was very different from Thursday's engine disintegration, the most serious midair incident involving the A380 since it debuted in 2007.
The 747-400 is a much older plane with an "entirely different" engine from the A380 even though they are both made by Rolls Royce, Voss said. The second engine failure was "much more routine," while the uncontained engine failure on the A380 was "more exceptional," Voss said.
He said it appeared credible that a design or construction flaw was the cause of the A380 engine failure.
Joyce, speaking to reporters on Saturday, said the 747-400 incident was nowhere near as significant as the A380 blowout.
"The one that was significant was the A380 in flight shutdown because this resulted in an uncontained explosion from the aircraft which caused damage to the wing," Joyce said.
"The engine on the 747 we've been operating for over 30 years. It's an engine that we have a lot of experience of, where the engines that are on the A380 are new engines, and because they are new ... we are obviously very cautious about the operation of that aircraft," he said.
Qantas' 747 fleet would not be grounded because of Friday's incident, he said. Qantas' six A380s won't fly until full safety checks are completed in the next few days, he added.
Maintenance failures are very rare in engines as new as the one that failed, which was built two years ago, he said. A foreign object would likely have caused visible damage to the engine's outside cover or the huge fan - or compressor - at the front of the engine.
Voss said it was most likely that the flight suffered a failure in the area that contains the turbine section and other rotating parts.
"This runs at extremely high temperatures and at very high, even supersonic, speeds," he said. "In that environment any minute manufacturing defect or a fault in the metallurgy such as microscopic cracks can lead to a failure."
Voss said that if the problem was shared by all Trent 900 engines, he believed it will be caught very quickly in inspections carried out by Qantas, Lufthansa and Singapore Airlines after Thursday's accident.
All of the airlines temporarily grounded their A380s, but Lufthansa and Singapore Airlines resumed flying them Friday after they passed safety inspections.
Airbus said it had asked all airlines operating the A380 planes with Rolls-Royce engines to carry out safety inspections "to ensure continuous safe operations of the fleet." Airbus has delivered a total of 37 of the A380s and the 17 operated by the airlines Emirates and Air France use engines from a different manufacturer.
The European Aviation Safety Agency has issued orders twice this year advising airlines about extra inspections or repairs needed to deal with potential problems with the Tret 900.
Joyce said such directives are commonplace - an airline could receive 100 per year across a range of planes - and that Qantas was in full compliance.
One August order indicated that routine wear could cause the turbine discs - rings the turbine blades are attached to - to come into contact withstationary parts of the engine, resulting in an in-flight shutdown, or even an oil fire.
But EASA spokesman Jeremie Teahan said the agency did not believe that problem could lead to a break-up of the type that occurred Thursday.
Nevertheless, a news media photo of engine debris indicates that a turbin disc may have failed, said John Goglia, a former National Transportation Safety Board member and an expert on aircraft maintenance.
A photo posted online by The Australian newspaper shows a turbine disc broken nearly in half, its blades missing. The location of the break appears to indicate that it was th disc that failed, Goglia said.
The photo also doesn't show any signs of discoloration on the disc that would indicate overheating, he said.
There are several reasons why a disc might fail, but they usually involve the metal used to make the disc or the manufacturing method, Goglia said. He cautioned hat he was looking at one photo, which was not enough information to make a definitive judgment.
Another Rolls Royce engine, the Trent 1000, also experienced an uncontained engine failure during testing in August for use on Boeing's 787 "Dreamliner." Boeing temporarily stopped shipments of the engines frm Rolls Royce, but the shipments have resumed, Boeing spokesman Jim Proulx said in an e-mail.
Proulx declined to elaborate on the circumstances of the engine failure, referring questions to Rolls Royce.
However, he said that based on recent findings during engine testing at a Rolls-Royce facility in Deby, England, a series of hardware and software improvements to the Trent 1000 are being incorporated before the first 787 delivery.
The Australian Transport Safety Bureau is leading an investigation into Thursday's incident with help from Qantas, Airbus, Rolls-Royce and aviation authorities in several counries.
Ian Sangston, the bureau's general manager of air safety investigation, said the faulty engine was being removed for inspection and the flight data and cockpit voice recorders were being analyzed in Australia.
Investigators also hoped to recover more than 100 pieces of debris, some as large as dors, scattered across Indonesia's Batam island. The agency will issue a preliminary report by Dec. 3, though the full investigation could take one year, Sangston said.
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